This invention relates to a system sensitive to a preselected one among a plurality of impinging light pulse trains, and more particularly to a light pulse discriminating system which may be used in proximity with one or more other light pulsing systems without being effected thereby.
Pulsed light systems for detecting target presence and/or range exhibit greater stability and less sensitivity to changes in ambient light conditions than steady state light level systems. Pulsed light systems such as the system disclosed in copending patent application Ser. No. 383,786 now issued as U.S. Pat. No. 3,867,628 are capable of sensing light pulses having predetermined frequency components to the exclusion of all other light pulse frequencies present including ambient light. Such pulsed light systems are sensitive to each other, however, and may not be used in proximity to each other without running the risk of system errors due to receipt of light pulses from more than one pulsed light source. Since it is often necessary to operate such light pulse sensing systems simultaneously in confined areas there is a need for a system having the capability of discriminating between those light pulses which are intended to be received for producing system output and those light pulses which must be ignored by the system to prevent the presence of output error created thereby.